Process for producing pressure-sensitive carbonless transfer sheets

Abstract

A pressure-sensitive carbonless transfer sheet comprising a paper substrate having a front and back surface and a coating composition adhered to at least one of the surfaces of the paper substrate. A novel process is provided for producing a pressure-sensitive carbonless transfer sheet which comprises the steps of preparing a hot melt suspending medium, the hot melt suspending medium being water insoluble and having a melting point of from about 60° C. to about 140° C. and a melting point range of less than about 15° C. A microencapsulated chromogenic material is prepared and dispersed in the hot melt suspending medium, the chromogenic material being a color precursor of the electron donating type. A coating dispersion is prepared by combining the hot melt suspending medium with the microencapsulated chromogenic color precursor material, the hot melt suspending medium being compatible with the color forming or developing characteristics of the chromogenic material. The coating dispersion is then applied to a substrate, the coating dispersion being applied at a coat weight of from about 1.0 pound to about 8.0 pounds per 3300 square feet of substrate at a coat thickness of from about 1 micron to about 50 microns. The coated substrate is set by cooling the coating dispersion.

What is claimed is: 
     
       1. A process for producing a pressure-sensitive carbonless transfer sheet comprising the steps of: (a) preparing a hot melt suspending medium, said hot melt suspending medium being water insoluble and having a melting point of from about 60° C. to about 140° C. and a melting range of less than about 15° C., said hot melt suspending medium being characterized by the presence of one or more functional groups selected from the group consisting of: carboxyl, carbonyl, hydroxyl, ester, amide, amine, heterocyclic groups and combinations thereof to impart polarity thereto, said hot melt suspending medium being further characterized by having a weight loss rating lf less than about 15 mg/g/hr. at 90° C. on a thermogravimetric scale when a 20.0 mg. sample of said hot melt suspending medium is analyzed and a heat resistance characteristic as measured by typewriter intensity decline on a seven day period of less than about 15 units loss when initial typewriter intensity is less than about 75 typewriter intensity units;   (b) preparing a microencapsulated chromogenic material, said chromogenic material being a color precursor of the electron donating type, said chromogenic material being mixed with a carrier oil to form an oil solution of said chromogenic color precursor material, said oil solution being microencapsulated by combination with a wall-forming compound selected from the group consisting of hydroxypropylcellulose, carboxymethylcellulose, gelatin, melamine-formaldehyde, polyfunctional isocyanates and prepolymers thereof, polyfunctional acid chlorides, polyamines, polyols, epoxides and mixtures thereof;   (c) preparing a coating dispersion by combining said hot melt suspending medium with said microencapsulated chromogenic color precursor material, said hot melt suspending medium being compatible with the color forming characteristics of said microencapsulated chromogenic material;   (d) applying said coating dispersion to a substrate, said coating dispersion being applied at a coat weight of from about 1.0 pounds to about 8.0 pounds per 3300 square feet of substrate; and   (e) setting said coated substrate by cooling said coating dispersion.   
     
     
       2. The process of claim 1 wherein said hot melt suspending medium includes a dispersing agent. 
     
     
       3. The process of claim 2 wherein said dispersing agent is an anionic dispersing agent selected from the group consisting of the sodium salts of condensed naphthalene sulfonic acids, the sodium salts of polymeric carboxylic acids, the free acids of complex organic phosphate esters, sulfated castor oil, poly (methyl vinyl ether/maleic anhydride) and mixtures thereof. 
     
     
       4. The process of claim 3 wherein said dispersing agent is added in an amount of from about 0.1% to about 10.0% based on the dry microcapsule weight. 
     
     
       5. The process of claim 1 wherein said color precursor is selected from the group consisting of: lactone phthalides, lactone fluorans, lactone xanthenes, leucoauramines, 2-(omega substituted vinylene) 3,3-disubtituted-3-H-idoles, 1,3,3,-trialkylindolinospirans and mixtures thereof. 
     
     
       6. The process of claim 1 wherein said hot melt suspending medium is selected from the group consisting of: deresinated, oxidized mineral waxes, amide waxes, fatty acids, hydroxylated fatty acids waxes, hydroxy stearate waxes, oxazoline waxes, amine waxes and mixtures thereof. 
     
     
       7. A process for producing a pressure-sensitive carbonless transfer sheet comprising the steps of: (a) preparing a hot melt suspending medium, said hot melt suspending medium being water insoluble and having a melting point of from about 60° C. to about 140° C. and a melting range of less than about 15° C., said hot melt suspending medium being a polar composition characterized by the presence of functional groups selected from the group consisting of: carboxyl, carbonyl, hydroxyl, ester, amide, amine, heterocyclic groups and combinations thereof, said hot melt suspending medium being further characterized by having a weight loss rating of less than about 15 mg/g/hr. at 90° C. on a thermogravimetric scale when a 20.0 mg. sample of said hot melt suspending medium is analyzed and a heat resistance characteristic as measured by typewriter intensity decline of a seven day period of less than about 15 units loss when initial typewriter intensity is less than about 75 typewriter intensity units;   (b) preparing a microencapsulated chromogenic material, said chromogenic material being a color precursor of the electron donating type selected from the group consisting of lactone phthalides, lactone fluorans, lactone xanthenes, leucoauramines, 2-(omega substituted vinylene) 3,3-disubstituted-3-H-indoles, 1,3,3-trialkylindolinospirans and mixtures thereof, said chromogenic material being mixed with a carrier oil to form an oil solution of said chromogenic color precursor material, said oil solution being microencapsulated by emulsification with a hydroxypropylcellulose wall forming compound and an poly isocyanate cross-linking agent:   (c) adding a dispersing agent to said microencapsulated chromogenic material, said dispersing agent being added in an amount of from about 0.1 percent to about 10.0 percent based on the dry weight of microencapsulated chromogenic material.   (d) preparing a coating dispersion by combining said hot melt suspending medium with said microencapsulated chromogenic material and said dispersing agent, said hot melt suspending medium being compatible with the color forming characteristics of said microencapsulated chromogenic material;   (e) applying said coating dispersion to a paper substrate, said coating dispersion being applied at a coat weight of from about 1.0 pounds to about 8.0 pounds per 3300 square feet of paper substrate; and   (f) setting said coated substrate by cooling said coating dispersion.   
     
     
       8. The process of claim 7 wherein said dispersing agent is an anionic dispersing agent selected from the group consisting of the sodium salts of condensed naphthalene sulfonic acid, the sodium salts of polymeric carboxylic acid, the free acids of complex organic phosphated esters, sulfated castor oil, poly (methyl vinyl ether/maleic anhydride) and mixtures thereof.